Hoist mechanism



Jan. 23, 1934. G LANDRY I I HOIST MECHANISM v Filed March 4, 19:52 sSheets-Sheet 1 ill I INVENTOR.

I BY M4 ATTORNEYcs.

Jan. 23, 1934. LANDRY 1,944,351

HOI ST MECHANISM Filed March 4. 1932 3 Sheets-Sheet 2 INVENTOR.

WWW

. ATTORNEY.

G. L. LANDRY HOIST MECHANISM Jan. 23, 1934.

Filed March 4, 1932 v 3 Sheets-Sheet 3 INVENTOR.

ATTORNEYos tion to provide an efiiclent two cylinder hydraulic PatentedJan. 23, 1934 um'rso STATES- norszr MECHANISM George Leo Landry,Milwaukee, Wis, assignor to The-Hell 09., Milwaukee, Win, a corporationof Wisconsin Application March 4, 1932. Serial No. 596,685 a 3 can. (Ci.138-4) The present invention relates in general to improvements in theart raising and lowering bodies and structures, and relates morespecificaliy to improvements in the construction and I operation 01 dualcylinder hydraulic hoist mechanisms for effecting relatively highvertical movements or certain types of structures.

An objectoi the invention is to provide improved fluid hoist mechanismwhich is simple l0 and durable in construction, and which is moreoverhighly eflicient and flexible in operation.

In the art of hauling certain materials in bulk, the trucks aresometimes equipped with bodies adapted to be elevated vertically withrespect to ii the chassis, to a relatively high degree in order that thebulk material may be permitted to gravitate from a. lower opening in thebody into a conveniently disposed container or chute. In i order toraise and lower the body vertically with respect to the chassis in thisclass of truck, various types or hoist mechanisms have been resorted to,but up ,to the present time no satisfactory vertical lift hydraulichoist for such bodies has been devised.

It is, therefore, an objector the present invenhoist mechanismapplicable, among other things, to high lift truck bodies, whichmechanism. will conditions.

A further object of the invention is to provide a two cylinder pumpactuated hydraulic hoist mechanism wherein the pump delivers fluid toonly one of the cylinders but the pistons of both of the cylinders arecaused to raise or lower uniformly and at the same time.

A iurther object of the invention is to provide a dual cylinder hoistoperated by a pump which delivers fluid to only one of the cylindera'thearrangement being such that when said cylinder is supplied with fluidits piston is raised and causes fluid above the piston in said cylinderto act as a displacement pump for raising the piston in the othercylinder, whereby both pistons travel equally.

A further object of the invention is to provide a dual cylinderhydraulichoist having a minimum of moving parts and which is easilycontrolled and which raises and lowers uniformly.

A further object 01' the invention is to provide a hydraulic hoist ofthe class described equipped with an oil reservoir and an automaticreplenish ing valve for the purpose of automatically refunctionemciently under all normal operating plenishina oil in one of thecylinders should leakage occur.

Another object of the invention is the provision of a dual cylinder pumpactuated hydraulic hoist which is extremely simple in construction andon operation, which is strong and durable, and which is well adapted forthe purposes set forth.

These and other objects and advantages will appear from the followingdetailed description.

A clear conception of the embodiment of the agnovel featuresconstituting the present invention and of the mode of constructing andof operating hoists built in accordance therewith, may be had byreferring to the drawings accompanying and forming a part of thisspeciflcationin which like reference characters designate the same orsimilar parts in the various views:

Fig. 1 is a side view of a truck having a vertically movable bodyoperable'by the improved hoist mechanism, the body being in its normal nlowered position and parts being broken away and in section to showdetails oi construction;

Fig. 2 is a view similar to Fig. i only showing the truck body and hoistmechanism in an ele-= vated position; go

Fig. 3 is a plan view of the truck chassis d the hoist mechanism;

Fig. i is a semi-schematic view showing in sec tion the improved hoistmech;

Fig. 5'is an enlarged, fragmentary, detail sec- 5 tio'nal viewillustrating the fluid supply tank and the replenishing valve associatedtherewith; and

Fig. 6 is an enlarged detail view, partly, in section, oithe pump andthe valve arrangement incorporated therein.

- Referring to Figs. 1, 2 and 3 of the drawings,

it will be observed that a truck body 8, which may be oi any of the welllmown types, is vertically'movably mounted on the rear portion of thechassis 9 01 the truck. The vertically movable mounting of the body isefiected by means oi vertical angle iron'posts 10 carried by thechassis, which are slldably engaged by complementary angle iron members11 secured to and depending irom the, body 8. For the purpose of wimparting upward movement to the body a, the improved dual cylinderhoisting mechanism is employed. In general, and as herein disclosed,

said hoisting mechanism comprises a rear cylinder 12, a forward cylinder13 of a larger circumference, movable elements or pistons 14 and 15associated with the cylinders 12, 13 respectively, a fluid supply tank16,-a pump 17, and tubular connections for efiecting transfer of fluidin. the system.

The rear cylinder 12 is supported vertically upon the rear portion ofthe chassis 9 and the forward cylinder 13 is also supported verticallyupon an intermediate portion of the chassis, and elongated piston rods18 and 19 extending vertically upwardly from the'pistons 14 and 15respectively, and through the upper ends of the cylinders 12 and 1 3,engage and are connected at their upper ends to brackets 20 and 21,respectively, carried by upper front and rear portions of the truck body8. The piston rod 19 is of considerably greater diameter than the pistonrod 18. The pump 17, which is preferably a gear or other positivedisplacement type of pump, is rigidly mounted on a transverse chassisbar 22 below the body in its lowered position, and the supply tank 16 ismounted in an elevated position adjacent the front portion of the body.The actuating fluid for the hoist mechanism, preferably oil, ispermitted to gravitate from the tank 16 to the inlet side of the pump 17through a supply pipe 23, and an automatic shut-off valve 24, within theinlet or suction side of the pump casing or in the pipe 23 immediatelythereadjacent, controls fluid flow into the pump.- A tubular connection25, having a lowering or by-passing valve 26 therein, leads from thepump 17 into a lower portion of the forward cylinder 13 below the piston15. It is also to be noted that an elongated pipe 27 extends from theupper portion of the forward cylinder 13 above its piston to the lowerportion of the rear cylinder 12, below, its piston. The pipe 27 isconnected to branch pipes 28, 28 leading respectively to the tank 16 andto the connection 25. Locatviiln each branch pipe 28, 28' is a valvecasing 29 which encloses valve mechanism which will be. referred to morein detailhereinafter. Another elongated tubular connection 30 aifordsdirect communication between the upper portion of the rear cylinder 12,above the piston 14, and the tank 16.

An important feature of the mechanism re-= sides in the fact that theforward cylinder 13 is of a diameter larger than that of the rearcylinder 12. The relationship of cylinder 13 to cyl-' inder 12, and ofpiston rod 19 to piston rod 18, must be such that the unobstructedcross-sectional area of thebore of cylinder 13 above the piston 15 mustequal the cross-sectional area of the bore of cylinder 12 below itspiston 14. This is for the reason that when fluid is forced intocylinder 13 below the piston 15 to elevate said piston, elevation ofsaid piston will displace fluid in the cylinder 13 above the piston andforce it through the pipe 27 into cylinder 12 below the piston 14 and byvirtue of the displaced fluid and the relative areas before mentioned,the piston 14 will be caused to elevate exactly equal to theelevation ofpiston 15 at all times and under all conditions.

The pump construction and the valve mechanism associated therewith isillustrated in detail in Fig. 6 and schematically in Fig. 4. It will beobserved that the suction line 23 from the tank enters the casing 17 andopens into a valve chamber 31 in which the automatic shut-off valve 24is movably disposed. A duct 32 leads from said chamber 31 into the gearchamber of the pump proper and another duct 33 in which is positioned abailcheck valve 34 extends from another portion of the gear chamber andis adapted, under certain operating conditions, to

discharge fluid into a port 35, from which the high pressure line 25(see Figs. 3 and 4) leads 31, while in another position said valve 26closes said ducts 37 and 38 so as to prevent by-pa'ssing of fluid, inwhich case, when valve 24 is positioned as shown in Fig. 6, the fluidmust pass through the gear chamber of the pump, as previously mentioned.The lowering or by-pass valve 26 is moved'from open to closed positionby manual control means which include an operating lever 39 extendinginto the cab of the truck (see Figs. 1 and 2) which is adapted to bepivotally moved to reciprocate a rod 40 extending to a lever 41 which isoperatively connected with said valve 26. On the other hand, theshut-off valve 24 is automatically operated and controlled by movementsof the truck body. Said shut-oil valve has connected thereto abell-crank lever 42 and to the free end of said-bell-crank lever one endof a link 43 is pivotally connected. The other end portion of said link43 is pivotally connected to a fixed bracket 44, and adjacent said endportion said link carries a flanged bracket 45., For the purpose ofcausing the body 8, when moved, to operate thevalve 24, a dependinglower front portion of the body may fixedly carry a tripping bar. It hasbeen found to be convenient in practice to secure a bar 46 transverselyto the front vertical angles 11 which move with the body, below thebody, and when the body is in lowered position said bar 46- engages anddepresses the flanged bracket 45, causing, through the link 43, themovement of the bell-crank lever 42 to the position shown in Fig. 1, inwhich position the valve 24 is as shown in Fig. 1 to allow fluid to flowthrough the gear chamber of the pump, but closing communication with theby-pass duct- 38. The flanged bracket 45 has secured thereto the lower.end portion of a vertical operating rod 47 which is slidably guided atits upper end portion in a suitable collar or bracket 48. When the body8 is elevated to its maximum position, a flange on the bar 46 engages afixed lug or projection 49 on the rod 47 to raise said rod, and throughthe connections 43 and 42 the valve 24 will be moved to shut offcommunication with the duct 32 to the pump gear chamber and to opencommunication ,with the by-pass 38.

To summarize, the operation of the improved hoist is as follows:Initially the body 8 is in its normal lowered position with respect tothe chassis illustrated in Fig. 1. In this position the shut-off valve24 is open with respect to the gear chamber of the pump, and the lowervalve 26 is in closed position. To set the hoist intooperation forelevating, a control lever 50 is moved to engage standard power take-oilmecha-- nism 52 with the vehicle transmission, and an elongated shaft51, extending to the gears of the r pump 17 is revolved to set the-pumpinto operation. The operation of the pump serves to draw fluid from thetank 16 through the pipe 23 into the suction port of the pump, throughthe pump chamber, and from thence out of the pump under 'piston 15 willraise the piston and will cause displacementof fluid in the cylinder 13above the piston.- This displaced fluid is conducted to the lowerportion of the smaller cylinder '12 through the pipe 27. Byvirtue of therelationship of the area of the space above the piston in cylinder 13 tothe area of the space below the piston 14 in cylinder 12, previouslydiscussed, the piston 14 is raised an amount equal to the elevation ofthe piston 15. Through the piston rods 18 and. 19 this elevation isimparted to the body 8. When the body reaches the maximum elevationshown in Fig. 2 the shut-off valve 2% is automatically closed withrespect to the gear chamber of the pump by the means previouslymentioned. Said shut-oil valve is, however, in

open position with respect to the by-pass duct 38 for the loweringvalve.

When it is desired to lower the truck body the operating lever 39 forthe lowering valve is manually moved, and through the connectionspreviously described the lowering valve 26 is moved from the positionshown in Fig. 6 to an open position with respect to the by-pass ducts 37and 38. Said lowering valve is thereby in direct communication with thehigh pressure side of the system and fluid will flow throughthe by-passductsirom the high pressure side of the system to-the suction side. Thisaction takes place during the descent of the body and'when the bodyreaches its normal lowered position the shut-off valve 24 will beautomatically opened with respect to the pump and closed with respect tothe by-pass ducts. The lowering valve is adjusted to its originalposition and everything is again in readiness for free circulation whenit is desired to again elevate the body.

After continued use of the hoist mechanism, it may be found that therings of the pistons 14, 15 no longer maintain a fluid tight joint, andthat leakage around these pistons occurs. Such leakage may result in thetendency of the rods 18, 19 to travel irregularly, and will preventuniform elevation of the body. In order to overcome this objection, thevalves housed within the casings 29 and disposed within the branch pipes28, 28, are provided. The branch pipe 28, as previously explained,connects the reservoir 16 with the fluid 28 is interposed between thefluid passages or connections 25, 27.

Each of the casings 29 is provided with a bore 53 having reducedcross-section at the upper portion thereof as at 54, andthe junction ofthe bored portions 53, 54 forms atapered valve seat 55 with which coactsa ball valve 56. In each of these valve mechanisms, the ball valve 56 isurged upwardly into closed position to shut off the flow of fluid, bymeans of a confined coiled spring 57.

When upward leakage past the piston 14 occurs, there will be a reductionin pressure above the piston 15 as compared to that existing below thispiston, when the pistons 14, 15 descend. This reduction in pressure willbe sufiicient to cause the upper ball check valve in the branch pipe 28,

to open, thus permitting fluid to flow from the tank .15 through thebranch pipe 28 and into the in the branch pipe 28', will automaticallybecome effective to deliver the excess oil or fluid from the connection27 to the connection 25, thereby likewise restoring the most desirablecondition of operation in the system.

. Although the improved duplex cylinder .hydraulic hoisting mechanismhas been specifically illustrated and described herein as being appliedto a high lift truck body, it is to be understood that the invention iscapable of more general application to hoisting mechanisms forstructures of various. types-wherein raising and lowering movements of abody are desired. Such' uses of the invention will obviously includemechanisms such as elevators, movable platforms, elevatable vehicleracks for chassis lubrication, and the like. It should also beunderstood that while the movable elements have been defined as pistons14, 15, these elements may partake various forms, and other types offluid pressure generating mechanisms than the gear pump-speciflcallyshown, may also be utilized without departing from the .scope of thisinvention.

Hoists manufactured in accordance with the present improvements haveproven highly successful and eificient in commercial operation, andwhile the actuating fluid utilized is preferably oil, it will beapparent that other fluids may be substituted. The prescnt'hoist isextremely practical for the elevation of bodies which are to be elevatedby supports disposed at two separated points, as said hoist permits theuse of hydraulic lifting power. which is advantageous over cables andmechanical means, and still insures the elevation of the body withoutany departure from the normal horizontal plane of thebody, which featurewill eliminate any possibility of binding during movements.

It should be understood that it is not desired to limit the invention tothe exact details of construction herein shown and described, forvarious modifications within the scope of the claims may occur'topersons skilled in the art.

What is claimed as the invention is:

1. In combination, primary and secondary cylinders each having a movablepiston, a fluid reservoir, a pump, an initial conduit connecting saidreservoir and said pump, a second conduit connecting said pump and saidprimary cylinder below its piston, a third conduit connecting saidprimary cylinder above its piston withysaid secondary cylinder below itspiston, a fourth conduit directly connecting said secondary cylinderabove its piston with said reservoir, and a fifth conduit connectingsaid reservoir with said third conduit. said fifth conduit havingtherein an automatic check valve for permitting fluid to howtherethrough only from said reservoir to said third conduit.

2. In combination, primary and secondary cylinders each having a movablepiston, a fluid reservoir, a pump, an initial conduit connecting saidreservoir and said pump. a second conduit connecting said pump andsaidprimary cylinder below its pistonfa third conduit connecting saidMil primary cylinder above its piston with said secondary cylinderbelow. its piston, a fourth conmatic check valve for permitting fluid toflow 'therethrough only from said third to said second conduit.

- 3. In combination, primary and secondary 'duit directly connectingsaid secondary cylinder above its piston with said reservoir, and afilth conduit connecting said reservoir and said third conduit andhaving therein-an automatic check valve for permitting fluid to flowtherethrough only from said reservoir to said third conduit, and

-a sixth conduit connecting said second and third conduits and havingtherein an automatic check valve for permitting fluid to flowtherethrough only from said third to said second conduit.

GEORGE LEO LANDRY.

